Lighting apparatus and projection type display, and driving method therefor

ABSTRACT

A lighting apparatus used for a projection type display is provided, which can change the incident ray volume to an optical modulation device without changing the optical output intensity of the lamp, and can exhibit excellent effects in expressive power of an image and adaptability to the use environment. The lighting apparatus of the present invention comprises; a light source, two fly-eye lenses constituting a uniform lighting device, and a shading plate arranged between these fly-eye lenses and constituting a dimming device for adjusting the amount of light of the outgoing light from the light source. The angle of inclination of the shading plate is controlled based on an image signal supplied to the optical modulation device, thereby enabling adjustment of the amount of light.

This is a Division of application Ser. No. 10/263,906 filed Oct. 4,2002. The entire disclosure of the prior application is herebyincorporated by reference herein in its entirety.

TECHNICAL FIELD

The present invention relates to a lighting apparatus, and a projectiontype display and a driving method therefor. More specifically, thepresent invention relates to a projection type display, which isexcellent in image expressive power and which can obtain images having abrightness which suits a use environment and a user's preference, and alighting apparatus used therefor.

BACKGROUND ART

Recent development of information equipment is remarkable, and demandfor thin displays having high resolution and low power consumption isincreasing with research and development advancing. Amongst these, theliquid crystal display for which the optical properties can be changedby electrically controlling the arrangement of the liquid crystalmolecules, is anticipated as a display that can correspond to the aboveneeds. As one form of such a liquid crystal display, a projection typeliquid crystal display (liquid crystal projector) is known, whichenlarges and projects an image emitted from an optical system using aliquid crystal light valve, onto a screen through a projection lens.

The projection type liquid crystal display uses a liquid crystal lightvalve as an optical modulation device, but a projection type displaywhich uses a digital mirror device (hereinafter referred to as DMD) asthe optical modulation device, instead of the liquid crystal lightvalve, has been put to practical use. However, this type of conventionalprojection type display has problems as described below.

-   (1) Due to leakage of light and stray light, which occur in various    optical elements constituting an optical system, sufficient contrast    cannot be obtained. Therefore, the gradient range (dynamic range)    which can be displayed is narrow, and the image quality and power is    inferior, as compared with an existing television receiver using a    cathode ray tube (hereinafter referred to as CRT).-   (2) Even if it is attempted to improve the image quality by various    kinds of image signal processing, since the dynamic range is fixed,    a sufficient effect cannot be demonstrated.

As a solution for the problems of the projection type display, that is,as a method of extending the dynamic range, it can be considered tochange the amount of light shone onto the optical modulation device(light valve) corresponding to the image signal. The simplest method forrealizing this is to change the optical output intensity of the lamp. Inthe projection type liquid crystal display, a method of controlling theoutput light of a metal halide lamp is disclosed in Japanese UnexaminedPatent Application, First Publication No. Hei 3-179886.

As a lamp used in the projection type liquid crystal display, ahigh-pressure mercury-vapor lamp is mainstream at present. However, itis quite difficult to control the optical output intensity with thehigh-pressure mercury-vapor lamp. Therefore, a method is desired inwhich the amount of incident light to the optical modulation device canbe changed corresponding to the image signal, without changing theoptical output intensity itself of the lamp.

Moreover, in addition to the above problems, since the brightness of alight source is fixed in the current projection type display, there areproblems in that the screen becomes too bright, for example, in a darkviewing environment, and that when the projection screen size is changedby the projection distance or zooming of a projection lens, thebrightness of the screen changes corresponding thereto.

DISCLOSURE OF THE INVENTION

The present invention has been achieved in order to solve the aboveproblems, with the object of providing a projection type display, whichcan change the amount of incident light to the optical modulation devicewithout changing the optical output intensity of the lamp, and canexhibit excellent effects in image expressive power and adaptabilitywith respect to a use environment, and a lighting apparatus usedtherefor.

In order to achieve the above object, the lighting apparatus of thepresent invention is a lighting apparatus used for lighting an opticalmodulation device in a projection type display, comprising: a lightsource, a uniform lighting device which equalizes the illuminancedistribution of light shone from the light source, and a dimming devicefor adjusting the amount of light emitted from the light source, whichis arranged on an optical axis of the light emitted from the lightsource, wherein the amount of light emitted from the uniform lightingdevice can be adjusted, by controlling the dimming device based oninformation from outside.

The present inventors have found that it is only necessary to add adimming device for adjusting the amount of light based on theinformation from outside to a conventional lighting apparatus, as ameans for adjusting the amount of light shone onto an area to be lightedcorresponding to an image, without changing the optical output intensityof the light source. The above “information from outside” includesinformation based on an image signal supplied to the optical modulationdevice, information based on a projection enlargement ratio, informationbased on the brightness under the use environment, and information basedon a user's preference.

In other words, according to the lighting apparatus of the presentinvention, the dimming device for adjusting the amount of light of theoutgoing beam from the light source is provided, and the dimming deviceis controlled based on the information from outside. Therefore, when theprojection type display is used, and when the information from outsideis, for example, information based on an image signal, the amount oflight of the outgoing beam from the light source is adjusted by theaction of the dimming device, such that the amount of light increaseswhen the image scene at that time is a bright scene, and the amount oflight drops when the image scene is a dark scene. In this manner, evenif the optical output intensity of the light source is constant, lighthaving a brightness corresponding to the image can be obtained in thearea to be illuminated, thus contributing to an extension of the dynamicrange of the projection type display. Similarly, a projectionenlargement ratio, brightness under the use environment, or light havinga brightness corresponding to the user's preference can be obtained.

As a specific form of the uniform lighting device, for example, there isa rod lens. In the present invention, however, there can be preferablyused one constituted of fly-eye lenses arranged sequentially from oneclose to the light source along the optical axis, and a convolution lensfor superimposing a plurality of secondary light source images formed bythe fly-eye lenses on the lighting plane. In the uniform lighting deviceusing the fly-eye lenses, a plurality of secondary light source imagesare formed by the fly-eye lenses, and the plurality of secondary lightsource images are superimposed by a second fly-eye lens and a condenserlens provided in the subsequent stage as the convolution lens, tothereby equalize the illuminance distribution of the original light ofthe light source.

As a specific form of the dimming device, there can be used one in whichthe dimming device comprises a shading member constructed such that atleast a part of the outgoing beam from the light source can be cut off,and the shaded area of the outgoing beam by the shading member can beadjusted.

According to this construction, the degree of shading of the outgoingbeam from the light source can be easily adjusted by the action of theshading member, and a dimming device suitable for the lighting apparatusof the present invention can be realized.

As the position for installing the shading member, three positions canbe considered, that is, between the fly-eye lens and the convolutionlens, on the outgoing side of the convolution lens, and between thefly-eye lens and the light source.

Particularly, when the shading member is provided between the firstfly-eye lens and the convolution lens, or on the outgoing side of theconvolution lens, it is desired that the shading member be arranged inthe vicinity of the focal point of each lens constituting the fly-eyelens.

The beams of light emitted from the fly-eye lens are once narrowed downin the vicinity of the focal point of each lens constituting the fly-eyelens. However, when the shading member is arranged here, extinction iscarried out in the area where the beams of light are narrowed down, andhence dimming can be carried out without affecting the illuminancedistribution in the area to be lighted. Since a gap corresponding to thefocal length of the fly-eye lens is provided beforehand in this portion,even if the shading member is arranged in the gap, it is not necessaryto change the optical arrangement of other parts.

As a specific form of the shading member, there can be exemplified onein which the shading member comprises a shading plate constructed so asto be able to move in the direction parallel with the principal planethereof, and the amount of light can be adjusted by the shift amount ofthe shading plate.

According to this construction, for example, some type of shading platedrive mechanism is provided on the shading plate to constitute a shadingplate capable of moving in a parallel direction, to thereby change theamount of light shaded by the shading plate. As a result, the amount oflight passing through the place where the shading plate is arranged canbe easily adjusted.

Alternatively, there can be exemplified one in which the shading membercomprises a shading plate constructed so as to be rotatable about arotation shaft extending in a parallel direction with the principalplane thereof, and the amount of light can be adjusted by the rotationangle of the shading plate.

According to this construction, for example, a stepping motor isconnected to the rotation shaft to rotate the shading plate, therebyenabling the amount of light passing through the place where the shadingplate is arranged to be adjusted easily and with good responsiveness.For example, if the shading plate is arranged such that the plate faceof the shading plate is parallel with the optical axis, thetransmittance of light can be brought to a value close to 100%. If theshading plate is rotated until the plate face of the shading plate has apredetermined angle with respect to the optical axis, extinction ispossible up to a minimum transmittance in a set range, and hence lighthaving a desired brightness can be obtained in the area to be lighted.

Preferably the shading member performs shading in linear symmetry withrespect to each of the beams of light emitted from the fly-eye lenses.More preferably, it is desirable to perform shading centrosymmetricallywith respect to the center of each beam of light.

As described above, in the vicinity of the focal point of each lensconstituting the fly-eye lens, the beams of light due to the pluralityof secondary light source images formed by the fly-eye lenses arenarrowed down. However, when the beams of light are shaded by using theshading member, the effect of equalization of the illuminancedistribution is hindered, if shading is performed excessively. To bespecific, for example, if all beams of light are shaded from one side,the illuminance distribution may have a polarization such that only oneside of the area to be illuminated becomes bright and the remainingother side is dark. As a countermeasure for this problem, if shading isperformed in linear symmetry with respect to an axis passing through thecenter of the beams of light, the illuminance distribution in the areato be illuminated becomes linearly symmetrical with respect to the axispassing through the center of the area to be illuminated. Therefore,even if the light having passed through the uniform lighting device hasa slight illuminance distribution, the appearance of a projected imagecan be improved, as compared with a case where the illuminancedistribution in the area to be illuminated has a polarization.

Moreover, if shading is performed centrosymmetrically with respect tothe center of each lens, a shading form well matched with theilluminance distribution of the original light of the light source canbe obtained, thereby enabling further equalization of the illuminancedistribution.

Furthermore, the shading member may have a construction such thatshading is performed in linear symmetry with respect to an axis passingthrough the center of the whole group of beams, instead of theconstruction in which shading is performed in linear symmetry withrespect to an axis passing through the respective centers of the beamsemitted from the fly-eye lenses. In this case, more preferably, shadingis performed centrosymmetrically with respect to the center of the wholegroup of beams.

In the case of this construction, the same action and effects can beobtained as in the case where shading is performed in linear symmetrywith respect to an axis passing through the center of each lens. Inother words, a polarization occurs in brightness due to shading, foreach of the secondary light source images, but by having thispolarization, the illuminance distribution in the area to be illuminatedwhere these secondary light source images are superimposed can be madeuniform.

As a specific means for performing shading symmetrically as describedabove, for example, a construction may be adopted comprising, forexample, the shading member arranged between the adjacent beams of lightemitted from the fly-eye lens, and two shading plates having a slitopening provided perpendicularly to the optical axis, and these twoshading plates are movable in a direction parallel with the respectiveprincipal planes and in an opposite direction to each other.Alternatively, the construction may be such that the shading membercomprises at least three shading plates provided perpendicularly to theoptical axis, and one of the at least three shading plates is fixed inposition, and the remaining shading plates located at a position oflinear symmetry with respect to the center line of the whole group ofbeams are movable in an opposite direction to each other.

In addition to the above construction, the lighting apparatus of thepresent invention may have a polarized beam splitter (hereinafterreferred to as PBS) array for equalizing the polarized state of theoutgoing beam from the light source in one direction, in the vicinity ofthe focal position of each lens constituting the fly-eye lens.

According to this construction, for example, when the lighting apparatusof the present invention is used in a projection type display such as aliquid crystal projector, in which display is performed by using onlylight in one polarized direction, the polarization of the outgoing beamfrom the light source can be converted so as to equalize thepolarization to that on the side used in the liquid crystal light valvein the PBS array. As a result, the use efficiency of the light can beincreased.

In this case, if two shading plates capable of moving in a paralleldirection are used as the shading member, at least one of the twoshading plates preferably serves as a shading plate which prevents theoutgoing beam from the light source from directly entering onto areflection film on the PBS array.

According to this construction, the apparatus configuration extendingfrom the PBS array to the shading member of the present invention can besimplified.

In the above construction, it is desirable to provide a second fly-eyelens on the incident side of the PBS array, and to provide a gap in atleast either one of between the second fly-eye lens and the shadingplate, and between the PBS array and the shading plate.

According to this construction, for example, cooling air can be made toflow in the gap, and the shading plate whose temperature has increasedby shading the strong beam from the light source can be cooled.

It is desired that the rotation shaft of the shading plate be arrangedat a place between beams of light emitted from the fly-eye lens.

According to this construction, the portion between respective beams ofthe plurality of beams of light emitted from the fly-eye lens is aportion where the light collected by the fly-eye lens does not reach.Therefore, when the rotation shaft is arranged in this position, and theshading plate is positioned so that the plate face of the shading platebecomes parallel with the optical axis, the beam is hardly cut off, andthe brightness does not drop when dimming is not performed.

Needless to say, the shading plate may have uniform transmittance oflight overall, but may also have an area in which the transmittance oflight is partially different. Specifically, for example, the shadingplate is formed by a plate obtained by forming a metal thin film on aglass, and the film thickness may have a distribution. Alternatively,for example, when the shading plate is formed in a rectangular shape, acorrugation may be added to the edge, rather than forming in a simplelinear form.

As described above, when an area where the transmittance of light ispartially different is provided in the shading plate, shading isperformed in a random distribution with respect to each of the pluralityof secondary light source images created by the fly-eye lenses.Therefore, by superimposing these secondary light source images, thesedistributions blend with each other, to thereby equalize the illuminancedistribution, to increase the uniformity of illuminance in the area tobe illuminated.

The shading plate may be provided as only one, or a plurality of shadingplates may be arranged along a plane perpendicular to the optical axis.

When a plurality of shading plates is arranged, the size of each shadingplate can be made small. Hence, it becomes possible to arrange theshading plate close to the focal position of each lens constituting thefly-eye lens. As a result, dimming can be performed without affectingthe illuminance distribution in the area to be illuminated. If a smallshading plate is used, it can be inserted in the existing uniformlighting device without changing the arrangement thereof, and thelighting apparatus does not become large.

Particularly, when a plurality of shading plates is arrangedcorresponding to each row of beams of light emitted from the fly-eyelens, the size of the shading plate can be made smallest, and hence theabove described effects can be reliably obtained.

Moreover, when a plurality of shading plates is rotated in an oppositedirection to each other centering on a center line of the group of beamsemitted from the fly-eye lens, thus resulting in shading in linearsymmetry with respect to the center of the whole group of beams, moreuniform lighting can be obtained.

When a plurality of shading plates is provided, the construction may besuch that these shading plates are rotated all at once with the sameangle. However, a construction in which only a part of the shadingplates is rotated and the remaining shading plates are left to standstill, or a construction in which a plurality of shading plates isrotated with a different rotation angle, or a construction combiningthese may be used to perform dimming.

According to these constructions, more delicate dimming can beperformed.

When the location of the shading plate is between the fly-eye lens andthe light source, since the illuminance distribution of the light sourceis originally large, then even if the shading plate is inserted betweenthe fly-eye lens and the light source, the illuminance distribution isnot largely affected. Hence, the illuminance distribution in the area tobe illuminated can be made small.

Moreover, when the shading plate is arranged in this position, theconstruction in which a plurality of shading plates is arranged alongthe plane perpendicular to the optical axis, or only a part of shadingplate of the plurality of shading plates is rotated, or the plurality ofshading plates is rotated with a different rotation angle can beadopted, as in the above described case (in which the shading plate isarranged between the fly-eye lens and the convolution lens). Also inthese cases, the same effects as above can be obtained. When a pluralityof shading plates is used in this arrangement, the distance between thelight source and the uniform lighting device can be reduced, and hencethe apparatus can be made small.

Furthermore, when a plurality of shading plates is arranged, theseshading plates may be formed so as to be able to rotate integrally aboutone axis of rotation, instead of separately driving these shadingplates.

According to this construction, even if the number of shading plates isplural, only one rotation shaft is required, and hence the apparatusconfiguration including the rotation mechanism can be simplified.

Moreover, the size and pitch of the plurality of shading plates may beuniform, or may be different depending on the location.

In this manner, by optimizing the overall design of the shading plates,the illuminance distribution in the area to be illuminated can befavorably maintained.

As described above, if the rotation shaft of the shading plate isarranged so as to follow the boundary of a plurality of lensesconstituting the fly-eye lens, an effect can be obtained that thebrightness does not drop when dimming is not performed. However, whenthe rotation shaft of the shading plate is inclined with respect to thearrangement direction of a plurality of lenses constituting the fly-eyelens, there is a place where the rotation shaft always goes across thecenter of the lens. Hence, there is concern that the brightness may dropslightly, even if dimming is not performed. However, in thisconstruction, shading is performed in a different area depending on eachlens, and hence when the images are superimposed, the illuminancedistribution is equalized, and the uniformity of illuminance in the areato be illuminated can be increased, as in the case where the corrugationis added to the edge of the shading plate.

With regard to shading using the shading member, if the light isreflected on the surface of the shading member, the reflected light mayadversely affect the display. By using a material having opticalabsorptivity at least on the surface irradiated by the light, of theshading member, unnecessary occurrence of reflected light can besuppressed, and the display quality can be enhanced. Since it is notnecessary to arrange the light absorbing material in other parts, theapparatus configuration becomes simple.

On the other hand, a material having optical reflectivity may be used atleast on the surface irradiated by the light, of the shading member. Inthis case, it is desirable to have a construction such that the shadingmember rotates so that the reflected light from the shading member isradiated outside of the lighting optical path.

According to this construction, the situation where the reflected lightfrom the shading member unnecessarily scatters to adversely affect thedisplay can be prevented.

When a shading member having optical reflectivity on the surface isused, it is desirable to have a construction such that a desired minimumtransmitted amount of light can be obtained with an angle such that thereflected light from the shading plate does not return to the lightsource.

According to this construction, the situation where the reflected lightfrom the shading member is reflected again by a reflector or the likeprovided in the light source, and unnecessarily scatters or interfereswith the beam of the light source, to thereby adversely affect thedisplay can be prevented.

When a shading member having optical reflectivity is used, it isdesirable to provide a light absorbing material for absorbing thereflected light at a position where the reflected light from the shadingplate reaches.

According to this construction, even in the case where a constituent ofthe lighting apparatus is arranged at a position where the reflectedlight from the shading plate reaches, a situation where the temperatureof the constituent increases to cause a problem can be avoided.

A projection type display of the present invention is a projection typedisplay having a lighting device, an optical modulation device whichmodulates the beam emitted from the lighting device, and a projectiondevice which projects the beam modulated by the optical modulationdevice, which comprises the lighting apparatus of the present inventionas the lighting device.

According to this construction, since the lighting apparatus which canobtain light having a desired brightness in the area to be illuminated,even when the optical output intensity of the light source is constant,is provided, the dynamic range of the projection type display can beextended. As a result, a projection type display, which is excellent inimage expressive power and adaptability to the use environment can berealized.

The driving device of the projection type display of the presentinvention preferably comprises: a control signal determination devicewhich determines a control signal which controls the dimming devicebased on an image signal per one frame constituting an image; a dimmingcontrol device which controls the dimming device based on the controlsignal; and an image signal extension device which extends the imagesignal based on the control signal.

According to this construction, a control signal for controlling thedimming device is determined based on the image signal per one frameconstituting an image, by the control signal determination device, andthen the dimming control device controls the dimming device based on thecontrol signal, to supply light to the optical modulation device, withthe brightness changing depending on the image, and the image signalextension device extends the image signal based on the control signal.By this operation, the dynamic range of the projection type display canbe extended, and a projection type display, which is excellent in imageexpressive power and adaptability to the use environment can berealized.

The driving method for a projection type display of the presentinvention is a driving method for the abovementioned projection typedisplay according to the present invention, wherein a control signal forcontrolling the dimming device is determined based on an image signalper one frame constituting an image, and the dimming device iscontrolled based on the control signal, to thereby adjust the amount oflight which illuminates the optical modulation device, and to extend theimage signal based on the control signal, and this extended image signalis supplied to the optical modulation device to thereby generate animage.

According to this construction, the dynamic range of the projection typedisplay can be extended, and an image having high image expressive powercan be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation view showing a schematic configuration of alighting apparatus according to a first embodiment of the presentinvention.

FIGS. 2A and 2B are respectively an elevation view showing the situationof a second fly-eye lens as seen from a shading plate side of thelighting apparatus according to the first embodiment of the presentinvention.

FIGS. 3A and 3B are respectively an elevation view showing the situationof a second fly-eye lens as seen from a shading plate side of a lightingapparatus according to a second embodiment of the present invention.

FIGS. 4A and 4B are respectively an elevation view showing the situationof a second fly-eye lens as seen from a shading plate side of a lightingapparatus according to a third embodiment of the present invention.

FIG. 5 is a side elevation view showing a schematic configuration of alighting apparatus according to a fourth embodiment of the presentinvention.

FIG. 6 is a side elevation view showing a schematic configuration of alighting apparatus according to a fifth embodiment of the presentinvention.

FIG. 7 is a side elevation view showing a schematic configuration of alighting apparatus according to a sixth embodiment of the presentinvention.

FIG. 8 is a side elevation view of the sixth embodiment of the presentinvention.

FIG. 9 is a diagram showing a schematic configuration of a projectiontype liquid crystal display in the first embodiment of the presentinvention.

FIG. 10 is a block diagram showing the construction of a driving circuitof the projection type liquid crystal display in the first embodiment ofthe present invention.

FIGS. 11A and 11B are diagrams for explaining a first method ofdetermining a brightness control signal from an image signal, in theprojection type liquid crystal display according to the first embodimentof the present invention.

FIG. 12 is a diagram for explaining a second method in the firstembodiment of the present invention.

FIG. 13 is a diagram for explaining a third method in the firstembodiment of the present invention.

FIG. 14 is a diagram showing the result of evaluation of the dimmingfunction of the projection type display, being an example of the presentinvention.

FIG. 15 is a side elevation view showing a schematic configuration of alighting apparatus according to a seventh embodiment of the presentinvention.

FIG. 16 is a side elevation view showing a schematic configuration of alighting apparatus according to an eighth embodiment of the presentinvention.

FIGS. 17A and 17B are enlarged plan views, showing a lighting apparatusaccording to the eighth embodiment of the present invention, taking outonly the portion of a second fly-eye lens and a PBS array, FIG. 17Ashowing a state where dimming is not applied, and FIG. 17B showing astate where dimming is applied.

FIGS. 18A and 18B are elevation views of a shading plate in the lightingapparatus according to the eighth embodiment of the present invention,FIG. 18A showing a state where dimming is not applied, and FIG. 18Bshowing a state where dimming is applied.

FIGS. 19A and 19B are elevation views showing another example of ashading plate according to the eighth embodiment of the presentinvention, FIG. 19A showing a state where dimming is not applied, andFIG. 19B showing a state where dimming is applied.

FIGS. 20A and 20B are enlarged plan views showing a lighting apparatusaccording to a ninth embodiment of the present invention, taking outonly the portion of a second fly-eye lens and a PBS array, FIG. 20Ashowing a state where dimming is not applied, and FIG. 20B showing astate where dimming is applied.

FIGS. 21A and 21B are elevation views of a shading plate in the lightingapparatus, FIG. 21A showing a state where dimming is not applied, andFIG. 21B showing a state where dimming is applied.

BEST MODE FOR CARRYING OUT THE INVENTION

[Projection Type Display]

One embodiment of the present invention will be described with referenceto the drawings.

At first, a projection type liquid crystal display, being one example ofa projection type display having the lighting apparatus of the presentinvention, will be described with reference to FIG. 9 through FIG. 13.

The projection type liquid crystal display of this embodiment is aprojection type color liquid crystal display of a three-plate type,comprising a transmission type liquid crystal light valve for each colorof R (red), G (green) and B (blue). FIG. 9 is a diagram showing aschematic configuration of this projection type liquid crystal display,wherein reference symbol 1 denotes a lighting apparatus, 2 denotes alight source, 3 and 4 denote fly-eye lenses (uniform lighting devices),5 denotes a shading plate (dimming device), 13 and 14 denote dichroicmirrors, 15, 16 and 17 denote reflection mirrors, 22, 23 and 24 denoteliquid crystal light valves (optical modulation devices), 25 denotes across dichroic prism, and 26 denotes a projection lens (projectiondevice).

The lighting apparatus 1 of this embodiment comprises the light source2, the fly-eye lenses 3 and 4, the shading plate 5 and a light absorbingbody 6. The light source 2 comprises a lamp 7 such as a high-pressuremercury lamp, and a reflector 8 for reflecting the light of the lamp 7.Moreover, as the uniform lighting device for equalizing the illuminancedistribution of the light of the light source in the liquid crystallight valves 22, 23 and 24, being an area to be illuminated, a firstfly-eye lens 3 and a second fly-eye lens 4 are sequentially arrangedfrom the light source 2 side. The first fly-eye lens 3 forms a pluralityof secondary light source images, and the second fly-eye lens 4 has afunction as a convolution lens for superimposing these images at theposition of the light valve. According to circumstances, a condenserlens for superimposing the secondary light source images may be arrangedat the position of the second fly-eye lens 4, or on the subsequent stagethereof. Hereinafter, explanation will be given for a case where thesecond fly-eye lens is used as the convolution lens. The second fly-eyelens 4 is used in combination with the PBS array described later, toform a polarization converting element.

In the case of this embodiment, the shading plate 5 is arrangedrotatably between the first fly-eye lens 3 and the second fly-eye lens4, as the dimming device for adjusting the amount of light of the beamemitted from the light source 2. The light absorbing body 6 is arrangedabove the first fly-eye lens 3 and the second fly-eye lens 4. Theconfiguration of the lighting apparatus will be described later indetail.

The construction of the subsequent stage of the lighting apparatus 1will be described, together with the action of each constituent.

The dichroic mirror 13 for reflecting blue light and green lighttransmits red light L_(R) of the beams of light from the light source 2,and reflects blue light L_(B) and green light L_(G). The red light L_(R)transmitted through the dichroic mirror 13 is reflected by thereflection mirror 17 and enters into the liquid crystal light valve forred color 22. On the other hand, the green light L_(G), of the coloredlight reflected by the dichroic mirror 13, is reflected by the dichroicmirror 14 for reflecting the green color, and enters into the liquidcrystal light valve for green color 23. On the other hand, the bluelight L_(B) transmits through the dichroic mirror 14, and enters intothe liquid crystal light valve for blue color 24, through a relay system21 comprising a relay lens 18, the reflection mirror 15, a relay lens19, the reflection mirror 16 and a relay lens 20.

The three colored lights modulated by the respective liquid crystallight valves 22, 23 and 24 enter into the cross dichroic prism 25. Thisprism is formed by bonding four rectangular prisms to each other, sothat a dielectric multilayer film for reflecting red light and adielectric multilayer film for reflecting blue light are formed in theinner face thereof in a cross shape. By these dielectric multilayerfilms, three colored lights are combined to form beams representing acolor image. The combined beams are projected onto a screen 27 by theprojection lens 26, being a projection optical system, and an enlargedimage is displayed.

The driving method for the projection type liquid crystal display 30 ofthis embodiment will be described below.

FIG. 10 is a block diagram showing the construction of a driving circuitof the projection type liquid crystal display 30 of this embodiment. Inthe case of a conventional projection type liquid crystal display havingno dimming function, the input image signal is directly supplied to aliquid crystal panel driver through suitable correction processing. Inthe case of this embodiment having a dimming function and controlling itbased on the image signal, a circuit such as DSP (1) to DSP (3), being adigital signal processing block, becomes necessary as a basicconstruction, as described below.

In this embodiment, as shown in FIG. 10, the image signal input as ananalog signal is input to the DSP (1) 32 (control signal determinationdevice), being a first digital signal processing circuit, through an ADconverter 31. The DSP (1) 32 determines a brightness control signal fromthe image signal. The DSP (2) 33 (dimming control device) controls adimming element driver 34 based on the brightness control signal, andfinally, the dimming element driver 34 actually drives a dimming element35 (in this embodiment, the shading plate 5).

On the other hand, the brightness control signal determined by the DSP(1) 32 is also input to the DSP (3) 36 (image signal extension device),together with the image signal. The DSP (3) 36 extends the image signalto a suitable gradation range, based on the brightness control signal.The image signal after the extension processing, is converted again tothe analog signal by a DA converter 37, and supplied from a panel driver38 to the liquid crystal light valve for the red color 22 (R panel inFIG. 10), the liquid crystal light valve for the green color 23 (G panelin FIG. 10), and the liquid crystal light valve for the blue color 24 (Bpanel in FIG. 10), respectively.

As for the control method of the lighting apparatus 1, there can beconsidered (1) display image adaptive control, (2) control by projectionenlargement ratio and (3) external control. The respective methods willbe described below.

(1) Display Image Adaptive Control

At first, a case is considered where the display image adaptive control,that is, a brightness control suitable for the display image is carriedout, such that in a bright image scene, the amount of light increases,and in a dark scene, the amount of light decreases. In this case, asdescribed above, the DSP (1) 32 determines the brightness control signalbased on the image signal. For this method, there can be considered, forexample, three methods as described below.

(a) Method in Which a Gradation Having Maximum Brightness, of the PixelData Included in an Observed Frame, is Designated as a BrightnessControl Signal.

For example, an image signal including gradations of 256 steps, from 0to 255, is assumed. It is assumed that when an optional frameconstituting continuous images is observed, the frequency distribution(histogram) for each gradation of the pixel data included in this frameshows a curve as shown in FIG. 11A. In the case of this graph, since thebrightest gradation included in the histogram is 190, this gradation 190is designated as the brightness control signal. This method can expressthe brightness most faithfully, with respect to the input image signal.

(b) Method in Which a Gradation of a Certain Proportion (for Example,10%) with Respect to the Frequency from the Maximum Brightness, from theFrequency Distribution (Histogram) for Each Gradation Included in theObserved Frame, is Designated as a Brightness Control Signal

For example, when the frequency distribution of an image signal is asshown in FIG. 12, an area of 10% is taken from the histogram from thebrightest side. If it is assumed that the gradation corresponding to 10%is 230, this gradation 230 is designated as the brightness controlsignal. As with the histogram shown in FIG. 12, when there is a suddenpeak in the vicinity of the gradation 255, if the above method (a) isadopted, the gradation 255 is designated as the brightness controlsignal. However, this sudden peak portion does not have much meaning asthe information for the whole screen. On the other hand, this method inwhich the gradation 230 is designated as the brightness control signalcan be said to be a method of judging the brightness control signal byan area having a meaning as information for the whole screen. Theproportion may be changed in the range of from about 2 to 50%.

(c) Method in Which a Screen is Divided Into a Plurality of Blocks, aMean Value of Gradations in Pixels Included in Each Block is Determined,and the Largest Value is Designated as the Brightness Control Signal

For example, as shown in FIG. 13, a screen is divided into m×n blocks, amean value of brightness (gradations) is calculated for each block,block A₁₁, . . . , A_(mn), and the largest value is designated as thebrightness control signal. It is desirable that the division number ofthe screen is from about 6 to 200. This method is one which can controlthe brightness, without detracting from the feeling of the whole screen.

In the above methods (a) to (c), the judgment of the brightness controlsignal can be performed with respect to the whole display area, or theabove methods may be applied only to a particular portion, for example,the central portion of the display area. In this case, control becomespossible so as to determine the brightness from a portion viewed by anaudience.

The DSP (2) 33 controls the dimming element driver 34 based on thebrightness control signal determined by the above methods. As thismethod, there can be considered the following three methods.

(a) Control Method in Real Time, Corresponding to the Output BrightnessControl Signal

In this case, since the brightness control signal output from the DSP(1) 32 is directly supplied to the dimming element driver 34, the signalprocessing in the DSP (2) 33 is not necessary. This method is ideal inview of completely following the image brightness. However, the contrastof the screen may change in a short cycle depending on the imagecontent, causing a problem in that the audience may feel unnecessarystress at the time of viewing.

(b) Method in Which an LPF (Low-Pass Filter) is Applied to the OutputBrightness Control Signal, and Control is Carried Out by the OutputThereof

For example, the changed portion of the brightness control signal of 1to 30 seconds is cut by the LPF, and the output thereof is used for thecontrol. According to this method, the changed portion for very shorttimes is cut, and hence a change in contrast in the above short cyclecan be avoided.

(c) Method of Detecting a Changeover Edge in the Brightness ControlSignal

The dimming element 34 is controlled only when there is a change largerthan a predetermined size (for example, at least 60 gradations) in thebrightness control signal. According to this method, it is possible toperform control corresponding to only a changeover of scenes.

In this manner, for example, when gradation 190 is determined as thebrightness control signal, and if it is assumed that the amount of lightof the maximum brightness (gradation 255) is 100%, the dimming element35 is driven so that an amount of light of 190/255=75% can be obtained.In this embodiment, the dimming element 35 is actually the shading plate5. Therefore, the shading plate 5 is rotated so that the transmittancebecomes 75% (shading rate is 25%). Similarly, when the gradation 230 isdesignated as the brightness control signal, the dimming element 35 isdriven so that an amount of light of 230/250=90% can be obtained.

On the other hand, the DSP (3) 36 extends the image signal to a suitablegradation range, based on the brightness control signal determined bythe DSP (1) 32 and the image signal. For example, when the image signalis extended up to the maximum gradation range, in the above example,since the displayable maximum gradation is 255, then when the brightnesscontrol signal is gradation 190 in the example of FIG. 11A, the imagesignal of gradations from 0 to 190 is extended to gradations from 0 to255, as shown in FIG. 11B. By such a control of the illumination lightamount and the extension processing of the image signal, a smoothgradation representation can be realized, while extending the dynamicrange of the image.

(2) Control by Projection Enlargement Ratio

Control is carried out corresponding to zooming of the projection lens26. Generally, since the amount of light per unit area in the liquidcrystal light valve (area to be lighted) is constant, there is atendency for the screen to become dark on the enlargement side, andbecome bright on the reduction side. Therefore, in order to correctthis, the dimming element 35 is controlled such that when the projectionlens 26 is changed to the enlargement side, the amount of lightincreases, and when the projection lens 26 is changed to the reductionside, the amount of light decreases.

(3) External Control

The dimming element 35 can be controlled by a user corresponding tohis/her preference. For example, the dimming element 35 is controlledsuch that in a dark viewing environment, the amount of light decreases,and in a bright viewing environment, the amount of light increases. Inthis case, the construction may be such that the user uses a controlleror directly operates the dimming element to carry out adjustment, orsuch that a brightness sensor is provided to automatically carry out thecontrol. In order to carry out the control of (2) and (3), however, thecircuits such as DSP (1) 32 to DSP (3) 36 in FIG. 10 are not necessary,but another circuit configuration is required.

[Lighting Apparatus-1]

The lighting apparatus in a first embodiment of the present inventionwill now be described, with reference to FIG. 1, FIG. 2A and FIG. 2B.

In this embodiment, an example of a lighting apparatus is shown in whicha shading plate is inserted between two fly-eye lenses constituting theuniform lighting device. FIG. 1 is a side elevation view showing theschematic configuration of the lighting apparatus according to thisembodiment. FIGS. 2A and 2B are respectively an elevation view showingthe situation of a second fly-eye lens as seen from the shading plateside of the lighting apparatus.

The lighting apparatus 1 of this embodiment comprises, as shown in FIG.1, a light source 2, fly-eye lenses 3 and 4, a shading plate 5 and alight absorbing body 6. The light source 2 comprises a lamp 7 such as ahigh-pressure mercury lamp, and a reflector 8 for reflecting the lightof the lamp 7. Moreover, the first fly-eye lens 3 and the second fly-eyelens 4 are sequentially arranged from the light source 2 side. Therespective fly-eye lenses 3 and 4 comprise a plurality of (in thisembodiment, for example, 6×8) lenses 9 and 10, and serves as the uniformlighting device for equalizing the illuminance distribution of lightemitted from the light source 2 in a liquid crystal light valve, beingan area to be lighted.

As the dimming device for adjusting the amount of light emitted from thelight source 2, one rectangular shading plate 5 is arranged rotatablybetween the first fly-eye lens 3 and the second fly-eye lens 4. Theshading plate 5 is arranged in the vicinity of the second fly-eye lens 4closer to the liquid crystal light valve, of the two fly-eye lenses 3and 4. The width W of the shading plate 5 is set to less than half of agap B between the two fly-eye lenses 3 and 4. A rotation shaft 11extending horizontally is provided at the center of the shading plate 5.A driving device (not shown) such as a stepping motor is connected tothe rotation shaft 11, so that the shading plate 5 can be rotated withhigh-speed response on receiving a drive signal from the dimming elementdriver 34.

The rotation shaft 11 of the shading plate 5 is arranged, as shown inFIG. 2A, parallel to the horizontal arrangement direction of a pluralityof lenses 10 constituting the second fly-eye lens 4, and along theboundary between adjacent lenses 10 (in FIG. 2A, between the fourth andfifth lenses from the top). The shading plate 5 comprises a material,for example, aluminum, steel, or stainless steel, and is formed suchthat in a rotated state, the side facing the light source 2 becomes areflecting surface 5 a, which reflects light emitted from the lightsource 2.

In FIG. 2A, the reflecting surface 5 a is located parallel to theoptical axis of the outgoing beam from the light source 2 (in FIG. 1, ina state where the outline of the shading plate 5 is shown by a two-dotchain line), so that the outgoing beam from the light source 2 istransmitted by 100% (in a state where no dimming is applied). On theother hand, in FIG. 2B, there is shown a situation in which the shadingplate 5 is rotated so that the reflecting surface 5 a faces the lightsource 2 from the state shown in FIG. 2A (in a stage where the outlineof the shading plate 5 is shown by a solid line), so that the outgoingbeam from the light source 2 is transmitted, for example, only by 30%(in a state where dimming is applied).

As shown in FIG. 1, the size of the shading plate 5 is set to give anangle such that if it is assumed that the desired minimum transmittedamount of light is 30%, when the shading plate 5 is inclined until thisminimum transmitted amount of light can be obtained, the reflected lightfrom the shading plate 5 does not return to the light source. At aposition outside the two fly-eye lenses 3 and 4 where the reflectedlight from the shading plate reaches at all times, regardless of thedegree of inclination of the shading plate 5, a light absorbing material6 comprising a nonflammable material and having a low opticalreflectance, such as asbestos, is arranged in order to absorb thereflected light.

According to the lighting apparatus 1 of this embodiment, the rotatableshading plate 5 is provided between the two fly-eye lenses constitutingthe uniform lighting device, and this shading plate 5 is rotated at ahigh speed, based on the image signal. Therefore, the amount of light isadjusted, for example, such that the amount of light increases in asituation where the image scene of the projection type display isbright, and the amount of light decreases in a situation where the imagescene of the projection type display is dark. Thereby, illuminationlight having a brightness corresponding to the image can be obtained inthe liquid crystal light valve, even if the optical output intensity ofthe light source 2 comprising a high-pressure mercury-vapor lamp, inwhich control of the optical output intensity is difficult, is constant,thereby contributing to an extension of the dynamic range of theprojection type display.

Since the shading plate 5 is arranged on the side close to the secondfly-eye lens 4, extinction is carried out at a portion where the beamsof light are narrowed down. Hence, dimming can be carried out withoutaffecting the illuminance distribution at the position of the liquidcrystal light valve. Moreover, since the rotation shaft of the shadingplate 5 is arranged along the boundary of the plurality of lenses 10constituting the second fly-eye lens 4, then in the state of 100%transmission as shown in FIG. 2A, the light is hardly cut off.Therefore, even in the construction where the shading plate 5 isinserted between the two fly-eye lenses 3 and 4, the brightness does notdrop when dimming is not performed.

Furthermore, in this embodiment, the shading plate 5 having opticalreflectivity is used. However, since it is constructed such that thedesired minimum transmitted amount of light can be obtained with anangle such that the reflected light from the shading plate 5 does notreturn to the light source 2, the situation where the reflected lightscatters unnecessarily or interferes to thereby adversely affect thedisplay can be prevented. Moreover, since the light absorbing material 6is provided at a position where the reflected light from the shadingplate 5 reaches even when an other constituent of the lighting apparatusis arranged at the position where the reflected light from the shadingplate 5 reaches, the situation where the temperature of the constituentincreases to cause a problem can be avoided.

[Lighting Apparatus-2]

A lighting apparatus according to a second embodiment of the presentinvention will be described with reference to FIGS. 3A and 3B.

The basic construction of the lighting apparatus of this embodiment isthe same as that of the first embodiment, and only the shape of theshading plate is different. Therefore, in this embodiment, only theshape of the shading plate is described, using FIGS. 3A and 3B, and thedescription for the common parts is omitted. FIG. 3A shows a state of100% transmission (a state in which dimming is not applied), and FIG. 3Bshows a state of 30% transmission (a state in which dimming is applied).

In the case of the first embodiment, the shape of the shading plate 5 isrectangular, and the upper and lower edges are formed linear. In thisembodiment, however, as shown in FIG. 3B, the shape of the shading plate40 is substantially rectangular, but a corrugation 40 a is added so thatthe upper and lower edges become wavy irregularly. Moreover corrugationis designed so that the side close to the first fly-eye lens becomesparticularly large, in the state with shading being performed.

When the shading plate 40 of this embodiment is provided, since shadingis performed in a random distribution with respect to each of theplurality of secondary light source images created by the first fly-eyelens 3, an image obtained by superimposing these images has a uniformilluminance distribution due to blending of these distributions, andhence the uniformity of illuminance at the position of the liquidcrystal light valve can be improved. Moreover, a larger effect can beobtained by having such a structure on the side close to the firstfly-eye lens 3, which forms secondary light source images. Since thelight emitted from the lamp has a centrosymmetric distribution withrespect to the optical axis, the effect can be increased by designingthe corrugation as described above.

The means for performing shading at a random distribution to obtain theabove effect includes; adding the corrugation to the shading plate,forming holes having different sizes and densities from the end of theshading plate, or partially providing areas having a different opticaltransmittance.

[Lighting Apparatus-3]

A lighting apparatus according to a third embodiment of the presentinvention will be described with reference to FIGS. 4A and 4B.

The basic construction of the lighting apparatus of this embodiment isthe same as that of the first and second embodiments, and only thearrangement of the rotation shaft of the shading plate is different.Therefore, in this embodiment, only the construction of the shadingplate is described, using FIGS. 4A and 4B, and the description for thecommon parts is omitted. FIG. 4A shows a state of 100% transmission (thestate in which dimming is not applied), and FIG. 4B shows a state of 30%transmission (the state in which dimming is applied).

In the case of the first embodiment, the rotation shaft 11 of theshading plate 5 is arranged so as to be parallel with the arrangementdirection of the plurality of lenses 10 of the second fly-eye lens 4,and to follow the boundary of the lenses 10. However, in thisembodiment, as shown in FIGS. 4A and 4B, the rotation shaft 42 of theshading plate 5 is inclined with respect to the arrangement direction ofthe plurality of lenses 10, and is arranged so as to cross each lens 10without following the boundary of the lenses 10.

As in the first and second embodiments, when the rotation shaft 11 ofthe shading plate 5 is arranged so as to match with the boundary of theplurality of lenses 10 of the second fly-eye lens 4, there is the effectthat the brightness does not decrease when dimming is not applied.However, as in this embodiment, when the rotation shaft 42 of theshading plate 5 is inclined with respect to the arrangement direction ofthe plurality of lenses 10 of the second fly-eye lens 4, there is aplace where the rotation shaft 42 crosses the center of the lens 10, andhence there is concern that the brightness may decrease slightly, evenif dimming is not applied. On the other hand, in this construction, asshown in FIG. 4B, shading is performed in different areas depending onthe lens (in FIG. 4B, the shape of the triangular portion of the lensfacing the other side of the shading plate 5 is different depending onthe lens), as in the second embodiment where a corrugation is added tothe edge of the shading plate. Therefore, when the images aresuperimposed, the illuminance distribution is equalized, and hence theuniformity of illuminance at the position of the liquid crystal lightvalve can be further improved.

[Lighting Apparatus-4]

A lighting apparatus according to a fourth embodiment of the presentinvention will be described with reference to FIG. 5.

This embodiment has also a common point with the first to the thirdembodiments in that the shading plate is inserted between two fly-eyelenses. The different point is that in the above embodiments, oneshading plate is used, but in this embodiment a plurality of shadingplates is used.

FIG. 5 is a side elevation view showing a schematic configuration of thelighting apparatus of this embodiment. In FIG. 5, common constituents tothose in FIG. 1 are denoted by the same reference symbols, and detaileddescription thereof is omitted.

In the lighting apparatus 44 of this embodiment, as shown in FIG. 5, aplurality of shading plates 45 a and 45 b is rotatably arranged betweenthe first fly-eye lens 3 and the second fly-eye lens 4, matched with aplane perpendicular to the optical axis. The plurality of shading plates45 a and 45 b is arranged in the vicinity of the second fly-eye lens 4,and the width of each of the shading plates 45 a and 45 b is set to beequal to or less than the width of each lens 10. A rotation shaft 11extending horizontally is provided at the center of each shading plate45 a, 45 b, and the rotation shaft 11 of each shading plate 45 a, 45 bis respectively arranged, matched with the boundary of the lenses 10. Adrive device such as a stepping motor is connected to the rotation shaft11 to separately rotate the shading plates 45 a and 45 b. Theconstruction may be such that each shading plate is associated with eachother and rotated all at once with the same angle, or only a part of theshading plates rotates, or the shading plates are rotated with differentrotation angles.

In FIG. 5, four shading plates 45 a, 45 b are shown, and the upper twoshading plates 45 a and the lower two shading plates 45 b rotate in theopposite direction to each other. That is to say, the shading plates 45a and 45 b, being two each on the upper and lower sides, rotatesymmetrically about the optical axis of the outgoing beam from the lightsource 2, so that their reflecting surfaces face outwards, the upper twoshading plates 45 a rotating counterclockwise in FIG. 5, and the lowertwo shading plates 45 a rotating clockwise in FIG. 5. In other words,shading is carried out in linear symmetry (up-down symmetry) withrespect to an axis passing through the center of the whole secondfly-eye lens 4 (with respect to an axis extending perpendicular to thepage in FIG. 5), by the four shading plates 45 a and 45 b. The size andthe number of the shading plates 45 a and 45 b are set so as to have anangle such that when the shading plates 45 a and 45 b are inclined untila desired minimum transmitted amount of light can be obtained, thereflected light from the shading plates 45 a and 45 b does not return tothe light source 2. A light absorbing material 6 a for absorbing thereflected light from the upper two shading plates 45 a, and a lightabsorbing material 6 b for absorbing the reflected light from the lowertwo shading plates 45 b are arranged, at a position outside of the twofly-eye lenses 3 and 4 where the reflected light from the shading plates45 a and 45 b reaches.

In this embodiment, by arranging the plurality of shading plates 45 aand 45 b, the size of each shading plate can be reduced. As a result,dimming can be carried out, while reducing the influence on theilluminance distribution at the position of the liquid crystal lightvalve. When a small shading plate is used, it can be inserted betweenthe first and second fly-eye lenses, without changing the arrangement ofthe existing first fly-eye lens and second fly-eye lens, and hence thelighting apparatus does not become large. Particularly in thisembodiment, since the width of each of the shading plates 45 a and 45 bis set to be equal to or less than the width of each lens 10, the sizeof the shading plate can be made sufficiently small, and hence the aboveeffect can be reliably obtained.

As described above, the plurality of shading plates 45 a and 45 b may berotated all at once with the same angle. However, if a construction inwhich only a part of the shading plates is rotated and the remainingshading plates are left to stand still, or a construction in which aplurality of shading plates is rotated with different rotation angles,or a construction combining these is employed, more delicate dimming canbe carried out.

Moreover, since shading is carried out in linear symmetry with respectto an axis passing through the center of the whole second fly-eye lens4, by the four shading plates 45 a and 45 b, the illuminancedistribution at the liquid crystal light valve becomes linearlysymmetrical with respect to an axis passing through the center of theliquid crystal light valve. Therefore, even if the beams after havingpassed through the second fly-eye lens 4 have a slight illuminancedistribution, the illuminance distribution is equalized by superimposingthe beams by the liquid crystal light valve. When the lighting apparatus44 of this embodiment is used for a projection type liquid crystaldisplay, in which only an image corresponding to the blue color isreversed with respect to the images of the other two colors, in thevertical direction or in the horizontal direction of the image, an imagein which the color balance is uniform at the opposite sides of thescreen 27 can be reproduced.

[Lighting Apparatus-5]

A lighting apparatus according to a fifth embodiment of the presentinvention will be described with reference to FIG. 6.

The different point in this embodiment from the lighting apparatus inthe first to fourth embodiments in which the shading plate is insertedbetween the two fly-eye lenses, is that the shading plate is insertedbetween the light source and the first fly-eye lens.

FIG. 6 is a side elevation view showing a schematic configuration of alighting apparatus of this embodiment. In FIG. 6, common constituents tothose in FIG. 1 are denoted by the same reference symbols, and detaileddescription thereof is omitted.

In the lighting apparatus 47 of this embodiment, as shown in FIG. 6, aplurality of shading plates 48 a and 48 b is rotatably arranged betweenthe light source 2 and the first fly-eye lens 3, along a planeperpendicular to the optical axis. A rotation shaft 11 extendinghorizontally is provided at the center of each shading plate 48 a, 48 b,and the rotation shaft 11 of each shading plate 48 a, 48 b isrespectively arranged, matched with the boundary of the lenses 9. Adrive device such as a stepping motor is connected to the rotation shaft11 to separately rotate the shading plates 48 a and 48 b. Theconstruction may be such that each of the shading plates 48 a and 48 bis associated with each other and rotated all at once with the sameangle, or only the shading plates on one side rotate, or the shadingplates are rotated with different rotation angles.

In FIG. 6, two shading plates 48 a and 48 b are shown, and the uppershading plate 48 a and the lower shading plate 48 b rotate in theopposite direction to each other. That is to say, the upper and lowershading plates 48 a and 48 b rotate symmetrically about the optical axisof the outgoing beam from the light source 2, so that their reflectingsurfaces face outwards, the upper shading plate 48 a rotatingcounterclockwise in FIG. 6, and the lower shading plate 48 a rotatingclockwise in FIG. 6. The angle of the shading plates 48 a and 48 b isset such that when the shading plates 48 a and 48 b are inclined until adesired minimum transmitted amount of light can be obtained, thereflected light from the shading plates 48 a and 48 b does not return tothe light source 2. A light absorbing material 6 a for absorbing thereflected light from the upper shading plate 48 a, and a light absorbingmaterial 6 b for absorbing the reflected light from the lower shadingplate 48 b are arranged, at a position where the reflected light fromthe shading plates 48 a and 48 b reaches.

In the lighting apparatus 47 of this embodiment, the shading plates 48 aand 48 b are arranged between the light source 2 and the first fly-eyelens 3. Therefore, the size of the lighting apparatus may be increased,according to circumstances. On the other hand, since the illuminancedistribution of the light source 2 is relatively large, from thebeginning, there will be no large influence, even if the shading plates48 a and 48 b are inserted between the light source 2 and the firstfly-eye lens 3. If anything, since the shading plate is not requiredbetween the first fly-eye lens 3 and the second fly-eye lens 4, theilluminance distribution at the position of the liquid crystal lightvalve can be made small.

If such a construction is employed where a part of shading plates of theplurality of shading plates 48 a and 48 b is rotated, or the pluralityof shading plates are rotated with difference angles, more delicatedimming can be performed. Moreover, the construction in which theplurality of shading plates 48 a and 48 b is rotated in the oppositedirection, and the effect of arranging the light absorbing materials 6 aand 6 b at the position where the reflected light from the shadingplates 48 a and 48 b reaches are the same as in the above embodiments.

[Lighting Apparatus-6]

A lighting apparatus according to a sixth embodiment of the presentinvention will be described with reference to FIG. 7 and FIG. 8.

This embodiment also shows an example in which the shading plate isinserted between the light source and the first fly-eye lens, as in thefifth embodiment, but the different point is that a plurality of shadingplates are rotated integrally.

FIG. 7 and FIG. 8 are side elevation views showing a schematicconfiguration of a lighting apparatus according to this embodiment, FIG.7 showing a state of 100% transmission (a state in which dimming is notapplied), and FIG. 8 showing a state of 30% transmission (a state inwhich dimming is applied). In FIG. 7 and FIG. 8, common constituents tothose of FIG. 1 are denoted by the same reference symbols, and detaileddescription thereof is omitted.

In the lighting apparatus 50 of this embodiment, as shown in FIG. 7 andFIG. 8, a plurality of shading plates 51 a to 51 e are arranged along aplane perpendicular to the optical axis, between the light source 2 andthe first fly-eye lens 3. In the fifth embodiment, the rotation shaft isprovided for each shading plate, and each shading plate is separatelyrotated. On the other hand, in this embodiment, the plurality of shadingplates 51 a to 51 e are integrally rotated clockwise in the figure,about one rotation shaft 11 connected to the central shading plate 51 c.The size and the pitch of the individual shading plate 51 a to 51 e arenot equal, and are different depending on the location. A lightabsorbing material 6 is arranged for absorbing the reflected light, at aposition where the reflected light from the shading plates 51 a to 51 ereaches.

According to the construction of this embodiment, even if the number ofthe shading plates 51 a to 51 e is plural, only one rotation shaft andone rotation mechanism are required, and hence the apparatusconfiguration can be simplified. Moreover, the design of the wholeshading plates can be optimized, by making the size and pitch of theindividual shading plate 51 a to 51 e different depending on thelocation. As a result, the illuminance distribution at the position ofthe liquid crystal light valve can be favorably maintained.

[Lighting Apparatus-7]

A lighting apparatus according to a seventh embodiment of the presentinvention will be described with reference to FIG. 15. The configurationof the lighting apparatus of this embodiment is substantially the sameas that of the fourth embodiment shown in FIG. 5. FIG. 15 is a sideelevation view showing a schematic configuration of the lightingapparatus of this embodiment. In FIG. 15, common constituents to thosein FIG. 5 are denoted by the same reference symbols, and detaileddescription thereof is omitted.

In the case of the lighting apparatus 44 of the fourth embodiment, theplurality of shading plates 45 a and 45 b is arranged between the firstfly-eye lens 3 and the second fly-eye lens 4. However, in the lightingapparatus 44A of this embodiment, as shown in FIG. 15, a plurality ofshading plates 45 a and 45 b is arranged rotatably on the outgoing sideof the second fly-eye lens 4, matched with a plane perpendicular to theoptical axis. The plurality of shading plates 45 a and 45 b is arrangedin the vicinity of the second fly-eye lens 4, and the width of each ofthe shading plates 45 a and 45 b is set to be equal to or less than thewidth of each lens 10. The point that the rotation shaft 11 extendinghorizontally is provided at the center of each shading plate 45 a, 45 b,and the rotation shaft 11 of each shading plate 45 a, 45 b isrespectively arranged, matched with the boundary of the lenses 10 is thesame as in the fourth embodiment. In FIG. 15, four shading plates 45 aand 45 b are shown, and the upper two shading plates 45 a and the lowertwo shading plates 45 b rotate in the opposite direction to each other.In other words, shading is carried out in linear symmetry (up-downsymmetry) with respect to an axis passing through the center of thewhole second fly-eye lens 4 (with respect to an axis extendingperpendicular to the page in FIG. 5), by the four shading plates 45 aand 45 b.

In this embodiment, since the size of the respective shading plates canbe made small by arranging the plurality of shading plates 45 a and 45b, the same effects as those of the fourth embodiment can be obtained,that is: dimming can be performed, while reducing the influence thereofon the illuminance distribution at the position of the liquid crystallight valve; the shading plates 45 a and 45 b can be inserted, withoutchanging the arrangement of the existing first fly-eye lens 3 and secondfly-eye lens 4, and hence the lighting apparatus can be made small; theilluminance distribution is made symmetrical, and the appearance of theprojected image is improved; and an image can be reproduced such thatthe color balance is uniform on the opposite sides of the screen.

[Lighting Apparatus-8]

A lighting apparatus according to an eighth embodiment of the presentinvention will be described with reference to FIG. 16 to FIG. 19B.

The basic construction of the lighting apparatus of this embodiment isthe same as that of the first embodiment, but is different in that a PBSarray, being the polarization converting element, is provided on theoutgoing side of the second fly-eye lens. Also, it is different in thatthe shading plate is not a rotatable type as exemplified in the first toseventh embodiments, but is a sliding type.

FIG. 16 is a plan view showing the schematic configuration of thelighting apparatus of this embodiment. In FIG. 16, common constituentsto those in FIG. 1 are denoted by the same reference symbols, anddetailed description thereof is omitted. FIG. 17A and FIG. 17B areenlarged plan views showing the lighting apparatus, taking out only theportion of the second fly-eye lens and the PBS array, and FIGS. 18A and18B, and FIGS. 19A and 19B are respectively elevation views of theshading plate. FIG. 17A, FIG. 18A and FIG. 19A show a state wheredimming is not applied, and FIG. 17B, FIG. 18B and FIG. 19B show a statewhere dimming is applied.

In the lighting apparatus 80 of this embodiment, as shown in FIG. 16,FIG. 17A and FIG. 17B, the first fly-eye lens 3 and the second fly-eyelens 4 are sequentially arranged from the light source 2 side, and thePBS array 81 is arranged on the outgoing side of the second fly-eye lens4. In the PBS array 81, a polarization separation film 82 and areflection film 83 are alternately arranged, and a ½ wave plate 84 forconverting a predetermined linearly polarized light into a linearlypolarized light orthogonal thereto (for example, converting ppolarization into s polarization) is provided on the outgoing side ofthe polarization separation film 82. The PBS array 81 is normallyprovided with a shading plate for preventing the outgoing beam from thelight source 2 from directly entering into the reflection film 83. Inthis embodiment, however, a shading plate 85 serving as the dimmingdevice of the present invention also fulfils this function. The secondfly-eye lens 4 and the PBS array 81 are arranged with a predeterminedgap therebetween, and the shading plate 85 is arranged in this gap.

The outline of each lens 10 having a rectangular shape as seen in planview, which constitutes the second fly-eye lens 4, is shown by a two-dotchain line in FIG. 18A and FIG. 18B. In this embodiment, the shadingplate 85 comprises two shading plates 85A and 85B, which extendvertically along the boundary of the horizontally adjacent lenses 10,and are overlapped in a transmission direction of light. In thenon-dimming state, as shown in FIG. 17A and FIG. 18A, the two shadingplates 85A and 85B are completely overlapped on each other, and thecentral axis of the two shading plates 85A and 85B overlaps on theboundary of the laterally adjacent lenses 10. These shading plates 85Aand 85B are moved in parallel (slide) in a direction along the principalplane, by a drive mechanism (not shown) such as a stepping motor. Whendimming is applied, as shown in FIG. 17B and FIG. 18B, the two shadingplates 85A and 85B slide in a horizontally opposite direction to eachother by the same distance, to thereby shade a predetermined area at theopposite ends of the lenses 10. For example, while the shading plate 85Aon the second fly-eye lens 4 side moves leftward shown by an arrow inFIG. 18B (upward in FIG. 17B), the shading plate 85B on the PBS array 81side moves rightward (downward in FIG. 17B). By such operation of theshading plate 85, in the lighting apparatus 80 of this embodiment, thetwo shading plates 85A and 85B perform shading in left-right symmetry,with respect to the axis passing through the center of each lens 10 ofthe second fly-eye lens 4.

If it is assumed that only one side of each lens of the second fly-eyelens is shaded for all lenses, the illuminance distribution may have apolarization such that only one side of the screen is bright, and theremaining other side is dark. On the contrary, the lighting apparatus 80of this embodiment has the sliding type shading plate 85, and shading isperformed in left-right symmetry with respect to the axis passingthrough the center of each lens 10 of the second fly-eye lens 4.Therefore, the illuminance distribution at the liquid crystal lightvalve, being the area to be lighted, becomes left-right symmetrical withrespect to the axis passing through the center of the liquid crystallight valve. As a result, the appearance of the projected image can beimproved, without a polarization such that only one side of the screenis bright, and the remaining other side is dark.

Moreover, in view of the construction of the current projection typedisplay of a three-plate method, since the optical path of one color ofthree colors passes through a relay lens, only an image corresponding tothis one color has to be reversed vertically or horizontally withrespect to the other two color images. Therefore, if it is assumed touse a lighting apparatus which shades only one side of each lens in thesecond fly-eye lens, for example, in images corresponding to R and G,the right side of the image is bright and the left side is dark, and onthe other hand, in an image corresponding to B, the right side of thescreen is dark and the left side is bright, causing a problem in thatthe color balance changes on the right and left sides of the screen.However, according to the lighting apparatus 80 of this embodiment,since the illuminance distribution at the liquid crystal light valvebecomes linearly symmetrical with respect to the central axis, an imagehaving uniform color balance on the opposite sides of the screen can bereproduced.

In this embodiment, since the two shading plates 85A and 85B also serveas a shading plate which prevents the outgoing beam from the lightsource from directly entering into the reflection film 83 in the PBSarray 81, another shading plate is not necessary, and hence theapparatus configuration can be simplified. Moreover, since a gap isprovided between the second fly-eye lens 4 and the two shading plates85A and 85B, cooling air can be made to flow in this gap. Hence, byshading strong light from the light source 2, the shading plates 85A and85B whose temperature has risen can be cooled.

As shown in FIG. 18A and FIG. 18B, the edges of the shading plates 85Aand 85B extend linearly. However, instead of this shape, there may beused a shape, as shown in FIG. 19A and FIG. 19B, in which the verticallycentral portion of each lens 10 at the edges of the shading plates 87Aand 87B is depressed curvilinearly. Since the light emitted from thelight source 2 has a substantially centrosymmetrical illuminancedistribution at the position of the shading plate, the illuminancedistribution can be equalized on the screen by using the shading plates87A and 87B having such a shape.

[Lighting Apparatus-9]

A lighting apparatus according to a ninth embodiment of the presentinvention will be described with reference to FIGS. 20A and 20B andFIGS. 21A and 21B.

The basic construction of the lighting apparatus of this embodiment isthe same as that of the eighth embodiment, and a PBS array is providedon the outgoing side of the second fly-eye lens, and a shading plate isprovided between the second fly-eye lens and the PBS array. Therefore,illustration of the whole construction is omitted. The construction ofthe shading plate is slightly different from that of the eighthembodiment.

FIGS. 20A and 20B are enlarged plan views showing the lighting apparatusof this embodiment, taking out only the portion of the second fly-eyelens and the PBS array, and FIGS. 21A and 21B are elevation views of ashading plate. FIG. 20A and FIG. 21A show a state where dimming is notapplied, and FIG. 20B and FIG. 21B show a state where dimming isapplied.

As shown in FIGS. 20A and 20B, in the lighting apparatus of thisembodiment, a shading plate 95 is arranged between the second fly-eyelens 4 and the PBS array 81, as in the eighth embodiment. The point thatthe shading plate 95 extends vertically along the boundary of thehorizontally adjacent lenses 10 is the same as in the eighth embodiment.However, in this embodiment, a shading plate 95C on the PBS array 81side, of two shading plates 95R, 95L and 95C, is fixed in position, andarranged on the incident side of the reflection film 83 of the PBS array81. On the other hand, the shading plates 95R and 95L on the secondfly-eye lens 4 side are moved in parallel (slide) in a direction alongthe principal plane.

FIGS. 20A and 20B show the central portion of the second fly-eye lens 4,and only the shading plate along the boundary of the lenses, being thecenter of the whole second fly-eye lens 4, is composed of only oneshading plate 95C on the PBS array 81 side, with the position thereoffixed. In the state where dimming is not applied, as shown in FIGS. 20Aand 21A, the two shading plates 95R, 95L and 95C are completelyoverlapped, with the central axis of the two shading plates 95R, 95L and95C overlapping on the boundary of horizontally adjacent lenses. At thetime of dimming, as shown in FIGS. 20B and 21B, regarding the shadingplates 95R and 95L on the second fly-eye lens 4 side, formed so as to bemovable, the shading plate 95R located on the right side and the shadingplate 95L located on the left side, with respect to the central shadingplate 95C, slide horizontally in an opposite direction to each other bythe same distance, to thereby shade a predetermined area at the oppositeends of the lens 10. For example, while the right shading plate 95Rmoves leftward as shown by an arrow in FIG. 21B (in FIG. 20B, the lowershading plate moves upward), the left shading plate 95L moves rightward(in FIG. 20B, the lower shading plate moves downward). By such operationof the shading plate 95, in the lighting apparatus of this embodiment,the two shading plates 95R, 95L and 95C perform shading in left-rightsymmetry, with respect to the axis passing through the center of thewhole second fly-eye lens 4.

This embodiment is different from the eighth embodiment in that shadingis not performed in linear symmetry for each lens 10, but shading isperformed so as to be linearly symmetrical with respect to the wholesecond fly-eye lens 4. In this case, illuminance distribution occurs ineach lens 10 due to shading, but the illuminance distribution becomesuniform with respect to the image obtained by superimposing therespective beams of the lenses 10. As a result, the same effects asthose of the eighth embodiment can be obtained also in the lightingapparatus of this embodiment, that is, the appearance of the projectedimage can be improved, without a polarization such that only one side ofthe screen is bright, and the remaining other side is dark; and an imagehaving uniform color balance can be reproduced on the opposite sides ofthe screen.

In the eighth and ninth embodiments, an example of a shading plateextending vertically along the boundary of horizontally adjacent lenseshas been described. On the contrary, a shading plate may be provided,extending horizontally along the boundary of vertically adjacent lenses.Also in this case, a similar effects can be obtained. In FIG. 19A andFIG. 19B, shading plates 87A and 87B having edges of a shape such thatthe central portion of each lens is slightly depressed are shown.However, instead of this construction, for example, a shading platehaving a construction like a diaphragm of a camera may be provided, sothat the shape of the optical transmission area becomes close to a roundshape, thereby enabling the illuminance distribution on the screen to befurther equalized.

The technical range of the present invention is not limited to the abovedescribed embodiments, and can be variously changed without departingfrom the scope of the present invention. For example, the shape, number,and arrangement of the shading plate is not limited to those shown inthe embodiments, and can be variously changed. In the above embodiments,a shading plate having optical reflectivity is used, but a shading platehaving optical absorptivity may be used. In this case, aluminum appliedwith black alumite treatment can be used as the material for the shadingplate. In the above embodiments, an example of a projection type liquidcrystal display using a liquid crystal light valve as the opticalmodulation device has been described. However, it is also possible toapply the present invention to a projection type display using a DMD asthe optical modulation device.

EXAMPLE

The present inventors actually produced the lighting apparatus in thefirst embodiment, and evaluated whether the shading plate can realize adesired dimming function. FIG. 14 is a diagram showing the evaluationresult, wherein the relation between an angle of inclination of theshading plate and the brightness on the screen is shown. In FIG. 14, theX-axis plots an angle of inclination (degree) of the shading plate, and0 degree indicates a state where the direction of the shading plate isparallel to the optical axis. The Y-axis plots brightness (%) on thescreen face, being designated as 100%, when the angle of inclination ofthe shading plate is 0 degree.

As is obvious from FIG. 14, there is a trend that as the angle ofinclination of the shading plate increases from 0 degree, the brightnesson the screen drops from the vicinity of 100%, and it has found thatwhen the angle of inclination is 30 degree or more, the brightness onthe screen drops to about 30%. Therefore, according to the lightingapparatus of the present invention, it is demonstrated that beams havinga desired brightness can be obtained on the screen by controlling theangle of inclination of the shading plate.

INDUSTRIAL APPLICABILITY

According to the lighting apparatus of the present invention, even ifthe optical output intensity from the light source is constant, beamshaving brightness corresponding to an image can be obtained in an areato be lighted, thereby contributing to the extension of the dynamicrange of a projection type display. By using this lighting apparatus, aprojection type display having excellent effects in image expressivepower and adaptability to the use environment can be realized. Hence,the lighting apparatus of the present invention is industrially useful.

1. A lighting apparatus used for lighting an optical modulation devicein a projection type display, comprising: a light source, a uniformlighting device which equalizes the illuminance distribution of lightshone from the light source, and a dimming device for adjusting theamount of light emitted from the light source, which is arranged on anoptical axis of the light emitted from the light source, the dimmingdevice including a shading plate constructed such that at least aportion of light emitted from the light source is cut off, the shadedarea of the outgoing beam being adjusted by a movement of the shadingplate, the amount of light emitted from the uniform lighting devicebeing adjusted by controlling the dimming device based on theinformation from outside, and the shading plate being structured to bemovable in a direction parallel with the principal plane thereof, andthe amount of light being adjusted by the shift amount of the shadingplate.
 2. The lighting apparatus according to claim 1, the shading platebeing arranged between the fly-eye lens and the convolution lens.
 3. Thelighting apparatus according to claim 1, the shading plate beingarranged in the vicinity of the focal point of each lens constitutingthe fly-eye lens.
 4. The lighting apparatus according to claim 1, theshading plate being arranged on the outgoing side of the convolutionlens.
 5. The lighting apparatus according to claim 1, the shading plateperforming shading in linear symmetry with respect to each of the beamsof light emitted from the fly-eye lenses.
 6. The lighting apparatusaccording to claim 1, the shading plate performing shadingcentrosymmetrically with respect to each of the beams of light emittedfrom the fly-eye lenses.
 7. The lighting apparatus according to claim 1,the shading plate performing shading in linear symmetry with respect tothe center of a group of beams emitted from the fly-eye lenses.
 8. Thelighting apparatus according to claim 1, the shading plate performingshading centrosymmetrically with respect to the center of a group ofbeams emitted from the fly-eye lenses.
 9. The lighting apparatusaccording to claim 5, further comprising: another shading plate, the twoshading plates being arranged between adjacent beams of light emittedfrom the fly-eye lens, each of the shading plates has a slit openingprovided perpendicularly to the optical axis, and the two shading platesbeing movable in a direction parallel with the respective principalplanes and in an opposite direction to each other.
 10. The lightingapparatus according to claim 7, further comprising: at least two shadingplates, the at least three shading plates being provided perpendicularlyto the optical axis, one of the at least three shading plates beingfixed in position, and the remaining shading plates located at aposition of linear symmetry with respect to the center of the group ofbeams emitted from the fly-eye lens being movable in an oppositedirection to each other.
 11. The lighting apparatus according to claim1, the shading plate being arranged between the fly-eye lens and thelight source.
 12. The lighting apparatus according to claim 11, furthercomprising at least one shading plate, the shading plates being arrangedalong a plane perpendicular to the optical axis.
 13. The lightingapparatus according to claim 12, the size of each of the plurality ofshading plates or the pitch of the plurality of shading plates beingdifferent depending on the location.
 14. The lighting apparatusaccording to claim 1, at least the surface on the side irradiated by thelight, of the shading plate, having optical absorptivity.
 15. Thelighting apparatus according to claim 1, at least the surface on theside irradiated by the light, of the shading plate, having opticalreflectivity.
 16. The lighting apparatus according to claim 15, a lightabsorbing material for absorbing the reflected light being provided at aposition where the reflected light from the shading plate reaches.
 17. Aprojection type display having a lighting device, an optical modulationdevice for modulating beams emitted from the lighting device, and aprojection device for projecting the beams modulated by the opticalmodulation device, which comprises a lighting apparatus according toclaim 1, as the lighting device.
 18. A projection type display accordingto claim 17, further comprising: a control signal determination devicefor determining a control signal which controls the dimming device basedon an image signal; a dimming control device for controlling the dimmingdevice based on the control signal; and an image signal extension devicefor extending the image signal based on the control signal.
 19. Adriving method for a projection type display according to claim 17, acontrol signal for controlling the dimming device being determined basedon an image signal, and the dimming device being controlled based on thecontrol signal, to thereby adjust the amount of light which illuminatesthe optical modulation device, and to extend the image signal based onthe control signal, and the extended image signal being supplied to theoptical modulation device to thereby generate an image.
 20. A lightingapparatus used for lighting an optical modulation device in a projectiontype display, comprising: a light source, a uniform lighting devicewhich equalizes the illuminance distribution of light shone from thelight source, and a dimming device for adjusting the amount of lightemitted from the light source, the dimming device being rotationallyarranged on an optical axis of the light emitted from the light source,the dimming device including a shading plate constructed such that atleast a portion of light emitted from the light source is cut off, theshaded area of the outgoing beam being adjusted by a movement of theshading plate, and the amount of light emitted from the uniform lightingdevice being adjusted by controlling the dimming device based on theinformation from outside.
 21. The lighting apparatus according to claim1, the principal plane being perpendicular to the optical axis.